Alveolar soft part sarcoma. An ultrastructural and lmmunocytochemical investigation of its histogenesis

Abstract

Fourteen alveolar soft part sarcomas were studied using electron microscopic analysis and a battery of immunocytochemical procedures in order to critically assess the extent to which these methods could explain the histogenesis of the tumor. All the tumors were stained with antibodies against keratin, vimentin, S‐100 protein, Leu‐7, neuron‐specific enolase, desmin, muscle‐specific actin, myoglobin, smooth muscle myosin, and fast and slow myosins. Eight tumors stained for vimentin, eight for desmin, eight for neuronspecific enolase, two for muscle‐specific actin, and one for fast myosin. No reactivity was detected with the other antibodies. Electron microscopic study showed a consistent pattern of fine structure and clarified the mode of formation of the distinctive cytoplasmic crystals which were detected in all 14 tumors. Intermediate filaments were sparse and specific myofilaments were not detected. Alveolar soft part sarcoma has a myogenic phenotype and the cells show skeletal muscle differentiation but do not closely resemble any known prototypic normal cell.

Pathology of Alveolar Soft Part Sarcoma

“…The cytoplasmic endoplasmic reticulum is as a rule sparse, mitochondria are numerous, and Golgi apparatus is greatly developed [43]. The latter is associated with crystalloids or precrystallized electron-dense granules mentioned above both of which are membranebound [31,43,47].…”

“…Mitoses are few and necrosis rare. Other possible aspects are nuclear pseudoinclusions, cystic or myxoid changes, stromal sclerosis, calcification, and chronic inflammatory infiltrate [2,13,[42][43][44][45][46][47][48][49][50]. Rarely, some tumors display a high mitotic rate, polymorphism, spindling, and xanthomatous changes [9].…”

“…In electron microscopy, ASPS cells are poor in desmosomes and are lined by incomplete basement membranes in contact with capillaries [43,47]. The cytoplasmic endoplasmic reticulum is as a rule sparse, mitochondria are numerous, and Golgi apparatus is greatly developed [43].…”

“…Other possibly expressed markers with little significance in ASPS include desmin, actin [5][6][7][8][9][10][11][12]14], S-100 protein [21], NKIC3 [22], histiocytic marker CD68 KP1 [58], and vimentin [24]. Nuclear myogenin and MyoD1, cytokeratin, epithelial membrane antigen (EMA), chromogranin, synaptophysin, neurofilament, and glial fibrillary acidic protein (GFAP) are always negative [24,47,50]. The eventual clinical utility of standard immune complementary immunohistochemical tests in ASPS is yet to be determined.…”

Alveolar Soft Part Sarcoma

“…The popular use of immunohistochemistry beginning in the late 1970s allowed us for the first time to turn attention to these crystals by applying a host of antibodies to these tumors with variable and sometimes conflicting results. [5][6][7][8][9][10][11][12][13] The most celebrated of all theories regarding the alveolar soft part sarcoma was that it represented an unusual myogenous tumor closely related to a rhabdo-myosarcoma. 9,10 Numerous immunohistochemical studies, however, demonstrated muscle markers in less than half of ASPS.…”